Biological auto(chemi)luminescence imaging of oxidative processes in human skin

Oxidative processes present across all types of organisms cause the chemical formation of electronically excited species with subsequent ultra-weak photon emission termed biological autoluminescence. Thus, imaging of this luminescence phenomenon using ultra-sensitive devices potentially enables monitoring of oxidative stress in optically accessible areas of the human body, such as skin. Although most of the works explored oxidative stress induced by UV light, for chemically induced stress, there is no quantified imaging of oxidative processes in human skin using biological autoluminescence under the controlled extent of oxidative stress conditions. Furthermore, the mechanisms and dynamics of the biological autoluminescence from the skin are not fully explored. Here we demonstrate that different degrees of oxidative processes on the skin can be spatially resolved through non-invasive label-free biological autoluminescence imaging quantitatively. Additionally, to obtain insight into the underlying mechanisms, we developed and employed a minimal chemical model of skin based on a mixture of lipid, melanin, and water to show that it reproduces essential features of the response of real skin to oxidative stress. Our results contribute to novel, noninvasive photonic label-free methods for quantitative monitoring of oxidative processes and oxidative stress.